21261451 has 4 divisors (see below), whose sum is σ = 21428992. Its totient is φ = 21093912.

The previous prime is 21261433. The next prime is 21261463. The reversal of 21261451 is 15416212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21261451 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21261481) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 83580 + ... + 83833.

It is an arithmetic number, because the mean of its divisors is an integer number (5357248).

Almost surely, 2^21261451 is an apocalyptic number.

21261451 is a deficient number, since it is larger than the sum of its proper divisors (167541).

21261451 is a wasteful number, since it uses less digits than its factorization.

21261451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167540.

The product of its digits is 480, while the sum is 22.

The square root of 21261451 is about 4611.0140967037. The cubic root of 21261451 is about 277.0326565520.

Adding to 21261451 its reverse (15416212), we get a palindrome (36677663).

It can be divided in two parts, 21261 and 451, that added together give a palindrome (21712).

The spelling of 21261451 in words is "twenty-one million, two hundred sixty-one thousand, four hundred fifty-one".